1. Field of the Invention
The present invention generally relates to a method for mitigating reference, and more particularly, to a method for mitigating co-channel interference in a received signal.
2. Description of Related Art
In a wireless communication environment, a signal transmitted therein may receive co-channel interference when the signal transmitted of the band is the same as the band used in neighboring areas. Thus, the cellular structure adopted by an existing wireless communication system allows all the neighboring areas to use different bands, as shown in FIG. 1. FIG. 1 is a diagram of a cellular wireless communication system. Referring to FIG. 1, the areas A, B, C, and D all use different bands, and those areas using the same band are all separated by other areas. When the handheld device 110 is in the area A as shown in FIG. 1, a signal transmitted by an access point (AP) in the area A to the handheld device will not be interfered by signals in the neighbouring areas B, C, and D. Meanwhile, since those areas using the same band as the area A are all located far away. The co-channel interferences thereof have lower power and accordingly the signal received by the handheld device 110 will not be affected by the co-channel interference.
The method described above will reduce the band efficiency and accordingly will reduce the capacity of the system. However, some of the handheld devices may be disabled when the number of users in the system is increased. Thus, some existing communication systems adopt the structure as illustrated in FIG. 2 in order to increase the capacity of the system. FIG. 2 is a diagram of a cellular wireless communication system. Referring to FIG. 2, each area F uses the same band, and accordingly the signal transmitted between the AP and the handheld device 210 will be interfered by the neighbouring APs easily. Thus, with the cellular structure illustrated in FIG. 2, the receiver usually adopts a single antenna interference cancellation (SAIC) technique for mitigating the co-channel interference in a received signal.
Presently, a receiver usually adopts both the SAIC technique and a channel estimation technique for mitigating interference in a received signal. However, the performance of the receiver can be greatly improved when the co-channel interference is very serious, but the performance of the receiver may be degraded to even worse than that of a receiver without SAIC technique when the co-channel interference is very weak.
A switching mechanism is disclosed in U.S. Patent Publication No. 2007/0058709, wherein a receiver can dynamically switch between a SAIC equalizer and a maximum-likelihood sequence estimation (MLSE) equalizer. Moreover, this mechanism allows the receiver to select the SAIC equalizer or the MLSE equalizer to process a burst signal so that the performance of the receiver is improved.
A SAIC receiver is disclosed in U.S. Patent No. 2005/0152485, wherein the receiver calculates the correlation between a plurality of training sequences defined by the system and an interference signal determines the time difference between the interference signal and the desired signal according to the correlation, and then provides the time difference to a backend channel estimation unit.